Information playback systems frequently utilize a stylus for reading signals from the surface of an information record. A stylus may be formed of a very small diamond mounted and bonded to a metallic, typically, titanium, shank. In order to provide proper playing performance from the stylus, it is necessary to lap certain flat surfaces on the diamond. Such lapping operations must be closely controlled. Insufficient lapping results in a small flat of inadequate size and shape. Moreover, over lapping can extend into the titanium shank. Cutting the titanium shank can contaminate the lapping disc (typically termed a scaife). In extreme cases, the bond of the diamond to the titanium can be weakened. The problem is further complicated by the fact that it is desirable to use diamonds that are not oriented crystallographically. Since the lapping rate of a diamond can vary by as much as a factor of three to one, depending on the orientation of the diamond on the shank, there is a corresponding variation in the lapping time needed to develop properly the desired flat or facet. It is possible to remove the styli and inspect them optically several times during the lapping procedures, but such inspections are time consuming. It is desirable, therefore, to control accurately the lapping of the diamond.